Transporting services such as an Internet Protocol television (IPTV) service requires traffic engineering mechanisms for optimizing the use of resources, guaranteeing a quality of service appropriate to the service, and minimizing service outages in the event of failures. The Point-To-Multipoint Multi-Protocol Label Switching Traffic Engineering (P2MP MPLS-TE) technology is designed to do this. It allows a point-to-multipoint tree to be set up in a Multi-Protocol Label Switching (MPLS) communications network allowing reservation of resources. The associated protocol specified in the Internet Engineering Task Force (IETF) document RFC 4875 is an extension of the Resource Reservation Protocol-Traffic Engineering (RSVP-TE) protocol and allows MPLS trees known as LSP P2MP trees to be set up in which packets are routed explicitly. Such trees replicate traffic from a node known as the root node to a set of nodes known as leaf nodes that are then responsible for routing the traffic to the receivers. P2MP RSVP-TE explicit routing allows trees to be set up that minimize the cost in terms of bandwidth consumption; it further allows reservation of resources and therefore a guaranteed quality of service when routing packets.
To minimize the impact of a failure on a service and in particular on television pictures in an IPTV service, it is necessary to be able to reroute packets in less than fifty milliseconds. The P2MP MPLS-TE Fast Reroute (FRR) mechanism specified in the IETF document “draft-ietf-mpls-p2mp-te-bypass-01” relies on local backup trees bypassing the protected element; it therefore allows the above-mentioned level of security to be guaranteed in the event of a link or transit node failure in an LSP P2MP network.
In contrast, it does not allow fast rerouting of packets in a time compatible with services requiring a guaranteed quality of service in the event of failure of leaf nodes of a label-switched point-to-multipoint tree.
Below, references to a failure affecting a leaf node refer to a failure of the node itself or a failure of a link supporting a branch coming from it.